The semiconductor integrated circuit (IC) industry has experienced rapid growth. In addition to increases in functional density (e.g., the number of interconnected devices per chip area) and decreases in geometry size (e.g., the smallest component that can be created using a fabrication process), device speed is continuously increasing. The scaling down process for density increases and size decreases can aid increases in device speed since signal propagation may be through shorter structures.
Other approaches to increasing device speed have been advanced. One approach includes the incorporation of dissimilar materials in a device. For example, a material different from a material of a substrate may be epitaxially grown for source/drain regions of a transistor, such as a field effect transistor (FET). Use of the dissimilar material can increase carrier mobility in the transistor, thereby increasing the speed of operation of the device.
With the increased usage of dissimilar materials in devices and the decreased geometry size, new problems have arisen that may not have been detectable in devices with a larger size or may not have affected those devices with a larger size. It is within this context the following disclosure arises.